Cairo , Egypt -LRB- CNN -RRB- -- At least three people were killed and 174 injured during clashes in Egypt on Sunday , officials said , exactly one year after the country 's first democratically elected president came to power .

Protesters took the streets , demanding the resignation of President Mohamed Morsy . His supporters also rallied at what were mostly peaceful demonstrations .

However , at least one person was killed in Bani Suef , south of Cairo , when fighting broke out between the two sides , said Health Ministry spokesman Yehya Moussa . Two others were killed in Asuit , he said . All three suffered gunshot wounds .

Many Egyptians worried about tensions leading to a dramatic showdown .

`` Egypt is on the brink of a volcano , '' government-run newspaper Al-Akhbar said .

Anti-Morsy supporters divided

Anti-Morsy protesters have a wide range of views on why Morsy should go and how to eject him from office .

The Tamarod , or `` rebel , '' campaign , a large movement led by opponents of the president , has spent months collecting signatures on a petition calling for Morsy to step down and call new elections . Organizers helped push for Sunday 's protest .

But the opposition is made up of various groups and loose coalitions , and not all anti-Morsy protesters agree with the road map the Tamarod campaign is advocating .

Some anti-Morsy protesters are loyal to the ousted government of Hosni Mubarak , while others want the army to intervene and lead a transition similar to the revolt that removed Mubarak from power .

Applause greeted Egyptian military helicopters that flew over Cairo 's iconic Tahrir Square midday on Sunday during protests .

Morsy 's opponents stood their ground in the square , where protests two years ago helped topple Mubarak 's 29-year rule . This time , they 're hoping for the same fate for Morsy , as the chant most heard in the crowd was the word `` leave . ''

Ordinary citizens fed up with fuel shortages , power cuts , a collapsing economy and rising crime have also joined the protests .

Opinion : Get ready for Egypt 's ` second revolution '

Morsy supporters rally

Morsy 's supporters , however , say the president needs more time to tackle Egypt 's problems . Supporters gathered at the presidential palace in Tahrir Square and in Rabaa Al-Adawiya Square in Cairo 's eastern suburb of Nasr City on Sunday .

A sit-in that started on Friday continued in Rabaa Al-Adawiya Square , where thousands of supporters gathered in support of Morsy .

Demonstrator Rifaat Ali traveled from Upper Egypt to the capital with a message to Morsy 's opponents : `` Our patience has run out . Either you back off , or the only thing left to do is attack with one fist . ''

The tensions were n't limited to Cairo . Protests also erupted Sunday in Suez , Sharqia , El Monofia and Gharbiya , the state-run Ahram news agency said . And in the port city of Alexandria , so many people turned out that traffic virtually came to a standstill .

Fears of more violence

Before the death reported Sunday , clashes had already claimed at least eight lives , including associates of the Muslim Brotherhood whose offices came under attack .

Andrew Pochter , a 21-year-old American in Alexandria to teach children English , was stabbed to death Friday while watching the demonstrations , his family said .

The Kenyon College student wanted to improve his Arabic before returning to the United States .

`` He cared profoundly about the Middle East , '' his family said . Pochter was planning a career in the region in hopes of advancing the peace process .

An Egyptian man died from a gunshot wound to the head , the health ministry said .

Muslim Brotherhood under fire

The Muslim Brotherhood , whose leaders included Morsy before his election , has lost four members to violence in recent days .

On Sunday , a spokesman for the group said that its headquarters in Cairo fell under attack from between 100 and 150 `` thugs . '' They threw stones and Molotov cocktails , spokesman Gihad Haddad said .

Police in charge of protecting the building abandoned it , he said .

Two people were shot dead Thursday when armed men attacked Muslim Brotherhood offices in Zagazig , Morsy 's hometown , the spokesman said . The gunmen were shouting `` Down with Morsy '' during the assault .

State media reported that protesters demanding Morsy 's ouster ransacked the city 's offices of his Freedom and Justice Party , the Muslim Brotherhood 's political wing .

Hamdeen Sabahy , a leftist former presidential candidate , said he and others challenging the Egyptian government `` reject the violence ... and all the attacks on the -LRB- offices -RRB- of the Muslim Brotherhood or their party . ''

`` Peace is our weapon , '' Sabahy said in a video message posted Saturday .

He urged his followers to continue their demonstrations nationwide , saying , `` We are not fighting a rock , rather failing politics that do not meet the needs of the people . ''

Egyptian troops deployed to keep order after Brotherhood offices attacked

Economic woes

Since Morsy took office , Egypt 's already sour economy has plummeted further as investors pulled out of the country , and tourism has dropped .

At the same time , crime in Egypt has spiked . Some are calling for a return to the law and order they knew under Mubarak 's autocratic rule , carried out with the iron hand of the military .

Although Morsy gave a speech highlighting his achievements during his first year in office , opposition members said he did not address his shortcomings and called for snap presidential polls , a new government and constitutional amendments .

Army allowed to crack down

Last week , Defense Minister Abdel-Fattah El-Sisi said the army would , if necessary , `` prevent Egypt from slipping into a dark tunnel of civil unrest and killing , sectarianism and the collapse of state institutions . ''

His remarks raised the specter of a return to the powerful role the military played in domestic politics under Mubarak .

But Morsy is not Mubarak . He was democratically elected . That fact should be respected , his supporters say .

A history of violent crackdowns

In the past year , about 80 people have been killed during protests and other political violence largely attributed to Egyptian security forces , Amnesty International said .

The United States has approved the departure of embassy and consulate employees and their dependents because of the unrest , a senior State Department official said .

The State Department warned Americans to cancel all but essential travel to or within Egypt .

About 200 U.S. Marines in Sigonella , Italy , and Moron , Spain , have been put on alert as a precaution , according to two Obama administration officials .

Ben Wedeman , Reza Sayah , and Salma Abdelaziz reported from Cairo ; Holly Yan reported and wrote from Atlanta . CNN 's Amir Ahmed , Sima Shelbayah , Greg Botelho , Elise Labott and Barbara Starr also contributed to this report .

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NEW : Three people are killed during Sunday clashes , a spokesman says

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The Muslim Brotherhood reports its Cairo headquarters fall under attack

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Large crowds of anti-Morsy opponents chant `` leave '' at protests

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`` Either you back off , or the only thing left to do is attack with one fist , '' says a Morsy supporter